Lighting system using multiple colored light emitting sources and diffuser element

ABSTRACT

A light emitting apparatus has a radiation source for emitting multi-colored radiation. A diffuser material receives at least a portion of the multi-colored radiation emitted by the radiation source and converts the multi-colored radiation into forward transferred radiation and back transferred radiation. An optic device is coupled to the diffuser material and is adapted to receive the back transferred radiation and extract at least a portion of the back transferred radiation from the optic device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication Ser. No. 60/568,373, filed May 5, 2004 and to U.S.Provisional Application No. 60/636,123 filed Dec. 15, 2004, and is acontinuation-in-part application of co-pending U.S. application Ser. No.10/583,105, filed Jun. 15, 2006, entitled “High Efficiency Light SourceUsing Solid-State Emitter And Down-Conversion Material,” which is the371 National Phase of International Application No. PCT/US2005/015736,filed May 5, 2005, which was published in English under PCT Article21(2) as WO 2005/107420 A2. The contents of all of these applicationsare incorporated in their entirety by reference herein.

BACKGROUND OF THE INVENTION

Solid state light emitting devices, including solid state lamps havinglight emitting diodes (LEDs) and resonant cavity LEDs (RCLEDs) areextremely useful, because they potentially offer lower fabrication costsand long term durability benefits over conventional incandescent andfluorescent lamps. Due to their long operation (burn) time and low powerconsumption, solid state light emitting devices frequently provide afunctional cost benefit, even when their initial cost is greater thanthat of conventional lamps. Because large scale semiconductormanufacturing techniques may be used, many solid state lamps may beproduced at extremely low cost.

In addition to applications such as indicator lights on home andconsumer appliances, audio visual equipment, telecommunication devicesand automotive instrument markings, LEDs have found considerableapplication in indoor and outdoor informational displays.

With the development of efficient LEDs that emit short wavelength (e.g.,blue or ultraviolet (UV)) radiation, it has become feasible to produceLEDs that generate white light through down conversion (i.e., phosphorconversion) of a portion of the primary emission of the LED to longerwavelengths. Conversion of primary emissions of the LED to longerwavelengths is commonly referred to as down-conversion of the primaryemission. An unconverted portion of the primary emission combines withthe light of longer wavelength to produce white light.

Phosphor conversion of a portion of the primary emission of the LED chipis attained by placing a phosphor layer in an epoxy that is used to fillthe reflector cup, which houses the LED chip within the LED lamp. Thephosphor is in the form of a powder that is mixed into the epoxy priorto curing the epoxy. The uncured epoxy slurry containing the phosphorpowder is then deposited onto the LED chip and is subsequently cured.

The phosphor particles within the cured epoxy generally are randomlyoriented and interspersed throughout the epoxy. A portion of the primaryradiation emitted by the LED chip passes through the epoxy withoutimpinging on the phosphor particles, and another portion of the primaryradiation emitted by the LED chip impinges on the phosphor particles,causing the phosphor particles to emit longer wavelength radiation. Thecombination of the primary short wavelength radiation and thephosphor-emitted radiation produces white light.

Current state of the art phosphor-converted white LED (pc-LED)technology is inefficient in the visible spectrum. The light output fora single pc-white LED is below that of typical household incandescentlamps, which are approximately 10 percent efficient in the visiblespectrum. An LED device having a light output that is comparable to atypical incandescent lamp's power density necessitates a larger LED chipor a design having multiple LED chips. Moreover, a form of direct energyabsorbing cooling must be incorporated to handle the temperature rise inthe LED device itself. More particularly, the LED device becomes lessefficient when heated to a temperature greater than 100° C., resultingin a declining return in the visible spectrum. The intrinsic phosphorconversion efficiency, for some phosphors, drops dramatically as thetemperature increases above approximately 90° C. threshold.

U.S. Pat. No. 6,452,217 issued to Wojnarowski et al. is directed to ahigh power LED lamp or multiple LED lamp design for use in lightingproducts and a source of heat removal therefrom. It has LED die arrangedin a multi-dimensional array. Each LED die has a semiconductor layer andphosphor material for creation of white light. A reflector gathers andfocuses the light from each of the die to approximate a high power LEDlamp. FIG. 12 of the patent illustrates a multi-sided array which emitslight at angled ray trace paths. FIG. 19 of the patent illustrates theLED lamp head being angled.

U.S. Pat. No. 6,600,175 issued to Baretz et al. and U.S. PatentApplication Publication No. 2004/0016938 filed by Baretz et al. aredirected to solid state light emitting devices that produce white light.The '938 patent application publication is a continuation of the '175patent. The solid state light emitting device generates a shorterwavelength radiation that is transmitted to a luminophoric medium fordown conversion to yield white light. In FIGS. 2 and 6 of the patent,there is a spaced relationship between the LED and the luminophoricmedium. In FIG. 6, for example, light is emitted from the solid statedevice 82 of shorter wavelength radiation, preferably in the wavelengthrange of blue to ultraviolet. When luminophoric medium 90 is impingedwith the shorter wavelength radiation, it is excited to responsivelyemit radiation having a wavelength in the visible light spectrum in arange of wavelengths to produce light perceived as white.

U.S. Pat. No. 6,630,691 issued to Mueller-Mach et al. is directed to anLED device comprising a phosphor-converting substrate that converts afraction of the primary light emitted by a light emitting structure ofthe LED into one or more wavelengths of light that combine withunconverted primary light to produce white light. As shown in FIG. 1 ofthe patent, LED 2 is disposed on substrate 10 which is a phosphor. Asshown in FIG. 2 of the patent, reflective electrode 21 is disposed onthe surface of the LED. Some primary light emitted by the LED impingeson reflective electrode 21, which reflects the primary light backthrough the LED and through the substrate. Some of the primary lightpropagating into the substrate is converted into yellow light and someis not converted. When the two types of light are emitted by thesubstrate, they combine to produce white light. Utilizing a reflectiveelectrode improves the efficiency of the LED device by ensuring that theamount of primary light entering the substrate is maximized.

U.S. Patent Application Publication No. 2002/0030444 filed byMuller-Mach et al., which issued as U.S. Pat. No. 6,696,703 toMueller-Mach et al., is directed to a thin film phosphor-converted LEDstructure. FIG. 2 of the application shows an LED structure 2 and aphosphor thin film 21 on a surface of LED 2. The LED generates bluelight that impinges on phosphor film 21. Some light passes throughphosphor 21 and some is absorbed and converted into yellow light whichis emitted from phosphor 21. The blue and yellow light combine to formwhite light. In FIG. 3 of the application, a reflective pad 25 is on asurface of LED 2. Light from LED 2 is reflected by reflective pad 25back through LED 2 and into phosphor 21. Light is then combined, asshown in FIG. 2 of the patent. FIG. 4 of the patent uses two phosphorfilms 31, 33 that are separated from LED 2 by substrate 13. Film 31emits red light. Film 33 emits green light. Blue light emitted by LED 2passes through films 31, 33, which combines with the red and green lightto produce white light. In the embodiment of FIG. 5 of the application,LED device 50 includes a plurality of phosphor thin films 37 and 38. Adielectric mirror 36 is disposed between thin film 37 and substrate 13.The dielectric mirror 36 is fully transparent to the primary emission oflight emitting structure 2, but is highly reflective at the wavelengthof the emissions of the phosphor thin films 37 and 38.

U.S. Patent Application Publication No. 2002/0030060 filed by Okazaki isdirected to a white semiconductor light-emitting device provided with anultraviolet light-emitting element and a phosphor. The phosphor layerhas a blue light-emitting phosphor and a yellow light-emitting phosphor,mixedly diffused. The light-emitting device 3 is inside reflective case5. In FIGS. 2, 4, and 8 of the application, phosphor layer 6 is formedaway from light-emitting element 3. In FIG. 2 of the application showsphosphor layer 6 formed inside sealing member 7, which is formed from atranslucent resin. In FIGS. 4 and 8 of the application, the phosphorlayer is formed on the surface of sealing member 7.

U.S. Patent Application Publication No. 2002/0218880, filed byBrukilacchio, is directed to an LED white light optical system. As shownin FIG. 1 of the application, optical system 100 includes LED opticalsource 110, optical filter 120, reflector 130, phosphor layer 135,concentrator 140, a first illumination region 150, a second illuminationregion 170, and thermal dissipater 190. Optical filter 120 includes areflected CCT range and a transmitted CCT range. Optical energy that iswithin the reflected CCT range is prohibited from passing throughoptical filter 120 (e.g., via reflection). Optical energy that entersthe optical filter front face 121 from the phosphor layer back face 137that is in the reflected range of optical filter 120 is reflected backinto phosphor layer 135. Optical energy that is in the transmitted CCTrange of optical filter 120 transmits through filter 120 and interactswith reflector 130.

The reflector 130 is a reflective optical element positioned to reflectoptical energy emitted from the LED optical source back face 112 backinto LED optical source 110. The optical energy interacts with theoptical material and a portion of the optical energy exits LED frontface 111 and interacts with optical filter 120. The optical energy thencontinues into the phosphor layer, thereby providing a repeatingtelescoping circular process for the optical energy that emits from thephosphor layer back face 137. This repeating process captures opticalenergy that otherwise is lost. Concentrator 140 captures optical energyemitting out of the phosphor layer front face 136.

U.S. Patent Application Publication No. 2002/0003233 filed byMueller-Mach et al., which issued as U.S. Pat. No. 6,501,102 toMueller-Mach et al., are directed to a LED device that performs phosphorconversion on substantially all of the primary radiation emitted by thelight emitting structure of the LED device to produce white light. TheLED device includes at least one phosphor-converting element located toreceive and absorb substantially all of the primary light emitted by thelight-emitting structure. The phosphor-converting element emitssecondary light at second and third wavelengths that combine to producewhite light. Some embodiments use a reflective electrode on the surfaceof the light emitting structure and some do not. In embodiments that usea reflective electrode 21 (FIGS. 2, 3, 6, 7 of the application), asubstrate separates the light emitting structure from the phosphorlayers. That is, the light emitting structure is on one side of thesubstrate and a phosphor layer is on the other side of the substrate. Inembodiments that do not use a reflective electrode (FIGS. 4, 5 of theapplication), a phosphor layer is disposed on a surface of the lightemitting structure.

U.S. Pat. No. 6,686,691 issued to Mueller et al. is directed to atri-color lamp for the production of white light. The lamp employs ablue LED and a mixture of red and green phosphors for the production ofwhite light. As shown in FIG. 3, lamp 20 includes LED 22 which ispositioned in reflector cup 28. LED 22 emits light in a patternindicated by lines 26 and a phosphor mixture 24 is positioned in thepattern. It may be seen that some unabsorbed light emitted by LED 22reflects from walls of reflector cup 28 back to phosphor mixture 24.Reflector cup 28 may modify light pattern 26, if light is reflected intoa space not previously covered by the initial light pattern. The wallsof the reflector cup may be parabolic.

U.S. Pat. Nos. 6,252,254 and 6,580,097, both issued to Soules et al.,are directed to an LED or laser diode coated with phosphors. The '097patent is a division of the '254 patent. More particularly, the patentsdisclose a blue-emitting LED covered with a phosphor-containingcovering. The phosphor-containing covering contains green-emittingphosphors and red-emitting phosphors. The green and red phosphors areexcitable by the blue-emitting LED.

U.S. Pat. No. 6,513,949 issued to Marshall et al., U.S. Pat. No.6,692,136 issued to Marshall et al., and U.S. Patent ApplicationPublication No. 2002/0067773 filed by Marshall et al. are directed to anLED/phosphor/LED hybrid lighting system. The '136 patent is acontinuation of the '949 patent. The '773 patent application issued asthe '136 patent. As shown in FIG. 1A, LED 10 includes an LED chipmounted in a reflective metal dish or reflector 12 filled with atransparent epoxy 13. FIG. 1B schematically depicts a typicalphosphor-LED 14 which is substantially identical in construction to theLED of FIG. 1A, except that the epoxy 18 filling the reflector 16contains grains 19 of one or more types of luminescent phosphormaterials mixed homogeneously therein. The phosphor grains 19 convert aportion of the light emitted by LED chip 15 to light of a differentspectral wavelength. The system permits different lighting systemperformance parameters to be addressed and optimized as deemed importantby varying the color and number of the LEDs and/or the phosphor of thephosphor-LED.

U.S. Pat. No. 6,603,258, issued to Mueller-Mach et al., is directed to alight emitting diode device that produces white light by combiningprimary bluish-green light with phosphor-converted reddish light. TheLED is mounted within a reflector cup that is filled with aphosphor-converting resin. Primary radiation emitted by the LED impingeson the phosphor-converting resin. Part of the primary radiationimpinging on the resin is converted into reddish light. An unconvertedportion of the primary radiation passes through the resin and combineswith the reddish light to produce white light.

U.S. Pat. No. 6,616,862, issued to Srivastava et al., is directed tohalophosphate luminescent materials co-activated with europium andmanganese ions. FIG. 3 of the patent discloses an LED mounted in cup 120having a reflective surface 140 adjacent the LED. The embodimentincludes a transparent case 160 in which phosphor particles 200 aredispersed. Alternatively, the phosphor mixed with a binder may beapplied as a coating over the LED surface. A portion of blue lightemitted by the LED that is not absorbed by the phosphor and thebroad-spectrum light emitted by the phosphor are combined to provide awhite light source.

U.S. Pat. Nos. 6,069,440, 6,614,179, and 6,608,332, issued to Shimazu etal., are directed to a light emitting device comprising a phosphor whichconverts the wavelength of light emitted by a light emitting componentand emits light. These patents also disclose a display device usingmultiple light emitting devices arranged in a matrix. These patents arerelated because they flow from the same parent application.

U.S. Pat. No. 6,580,224 issued to Ishii et al. is directed to abacklight for a color liquid crystal display device, a color liquidcrystal display device, and an electroluminescent element for abacklight of a color liquid crystal display device.

U.S. Patent Application Publication No. 2002/0167014 filed by Schlerethet al., which issued as U.S. Pat. No. 6,734,467 to Schlereth et al., aredirected to an LED white light source having a semiconductor LED basedon GaN or InGaN which is at least partly surrounded by an encapsulationmade of a transparent material. The transparent material contains aconverter substance for at least partial wavelength conversion of thelight emitted by the LED. The LED has a plurality of light-emittingzones by which a relatively broadband light emission spectrum isgenerated energetically above the emission spectrum of the convertersubstance.

A publication entitled “Optical simulation of light source devicescomposed of blue LEDs and YAG phosphor” by Yamada K., Y. Imai, and KIshii, published in Journal of Light and Visual Environment 27(2): 70-74(2003) discloses using light reflected from a phosphor as an effectiveway of obtaining high output from light sources composed of LEDs andphosphor.

SUMMARY OF THE INVENTION

A light emitting apparatus comprises a radiation source for emittingmulti-colored radiation. A diffuser material receives at least a portionof the multi-colored radiation emitted by the radiation source andconverts the multi-colored radiation into forward transferred radiationand back transferred radiation. An optic device is coupled to thediffuser material and is adapted to receive the back transferredradiation and extract at least a portion of the back transferredradiation from the optic device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing. It is emphasizedthat, according to common practice, the various features of the drawingare not to scale. On the contrary, the dimensions of the variousfeatures are arbitrarily expanded or reduced for clarity. Included inthe drawing are the following Figures:

FIG. 1 is a graph of relative output versus wavelength showing reflectedand transmitted spectral distribution of light for one type of phosphor(YAG:Ce);

FIG. 2 is a high efficiency light source that uses solid stateemitter(s) and down conversion material, in accordance with an exemplaryembodiment of the present invention;

FIG. 2A is an alternative embodiment of a high efficiency light sourcethat uses multiple colored light emitting sources and down conversionmaterial;

FIG. 2B is a cross-sectional view of a bottom portion of the highefficiency light source shown in FIG. 2A;

FIG. 3 is a cross-sectional view of a bottom portion of the highefficiency light source shown in FIG. 2;

FIG. 4 illustrates another high efficiency light source that usesmultiple solid state emitters and down conversion material, inaccordance with another exemplary embodiment of the present invention;

FIG. 5A is yet another embodiment of a high efficiency light source thatuses solid state emitter(s) and down conversion material, in accordancewith another exemplary embodiment of the present invention;

FIG. 5B is a cross-sectional view of the high efficiency light sourceshown in FIG. 5A;

FIG. 6 is an illustration of still another high efficiency light sourcethat uses solid state emitter(s) and down conversion material, inaccordance with an exemplary embodiment of the present invention;

FIG. 7 depicts a reflector surrounding the high efficiency light sourceshown in FIG. 6, for redirecting the rays emitted from the lightsource(s);

FIG. 7A illustrates another exemplary embodiment of the invention usingmultiple colored light emitting sources;

FIG. 7B illustrates a down conversion material dispersed in a downconversion material layer in accordance with an exemplary embodiment ofthe present invention;

FIG. 7C illustrates a down conversion material dispersed in a downconversion material layer in accordance with an alternative embodimentof the present invention;

FIG. 7D illustrates a down conversion material dispersed in a downconversion material layer in accordance with another alternativeembodiment of the present invention;

FIGS. 8A through 8E illustrate various geometric shapes for the opticalelement, or optical lens, disposed immediately above an exemplary lightemitting source, in accordance with different exemplary embodiments ofthe present invention;

FIGS. 8F and 8G illustrate other embodiments of a reflector and an opticdevice;

FIG. 9A shows a device having multiple high-efficiency light sourcesthat use solid state emitter(s) and down conversion material placed on alightpipe for redirecting the light rays from the light sources, inaccordance with an exemplary embodiment of the present invention;

FIG. 9B is a cross-sectional view of the device shown in FIG. 9A;

FIG. 9C illustrates a cross-section view of another alternativeembodiment of the device shown in FIG. 9A that may include multiplecolored light emitting sources;

FIG. 10A is an illustration of another device having multiple highefficiency light sources that use solid state emitter(s) and downconversion material disposed around edges of a lightpipe for redirectingthe light rays from the light sources, in accordance with an exemplaryembodiment of the present invention;

FIG. 10B is a cross-sectional view of the device shown in FIG. 10A;

FIG. 11 is an illustration of yet another high efficiency light sourcearranged so that it is surrounded by a reflector and a high efficiencymicrolens diffuser, in accordance with an exemplary embodiment of thepresent invention;

FIG. 11A is an illustration of an alternative embodiment of theembodiment illustrated in FIG. 11 that may include multiple coloredlight emitting sources;

FIG. 12 is an illustration of still another high efficiency light sourcedirecting radiation towards a down conversion material and a reflector,where the down conversion material is disposed between the highefficiency light source and the reflector, in accordance with anexemplary embodiment of the present invention;

FIG. 12A is an illustration of an alternative embodiment of theembodiment illustrated in FIG. 12 that may include multiple coloredlight emitting sources;

FIG. 13 is a schematic diagram depicting a high powered light emitterradiating light towards a down conversion material by way of an opticalelement, in accordance with an exemplary embodiment of the presentinvention; and

FIG. 14 is a diagram illustrating the exemplary radiation rays that mayresult when an exemplary radiation ray from a short-wavelength LED chipimpinges on a layer of down conversion material.

DETAILED DESCRIPTION OF THE INVENTION

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

FIG. 14 is a diagram illustrating the exemplary radiation rays that mayresult when an exemplary radiation ray 2000 from a short-wavelength LEDchip 2002 impinges on a layer of down conversion material 2004 which maybe a phosphor layer. The impingement of exemplary short-wavelengthradiation 2000 from a short-wavelength source such as an LED chip 2002onto a down conversion material layer 2004 may produce radiation withfour components: back transferred short-wavelength radiation 2006reflected from the down conversion material layer 2004; forwardtransferred short-wavelength radiation 2008 transmitted through the downconversion material layer 2004; forward transferred down-convertedradiation 2010 transmitted through the down conversion material 2004;and back transferred down-converted radiation 2012 reflected from thedown conversion material 2004. The four components may combine toproduce white light.

Two of the four components 2010 and 2012 may each be comprised of twosub-components. One of the sub-components of forward transferreddown-converted radiation may be emitted radiation 2014; i.e.,down-converted radiation having a longer wavelength than theshort-wavelength radiation that impinges onto the down conversionmaterial layer 2004. The emitted radiation sub-component 2014 of forwardtransferred down-converted radiation may be produced by short-wavelengthradiation 2000 impinging on particles of the down conversion material2004 as it is transmitted through the down conversion material 2004. Thesecond sub-component of forward transferred down-converted radiation maybe forward scattered emitted radiation 2016; i.e., other down-convertedradiation having a longer wavelength than the short-wavelength radiation2000 that impinges onto the down conversion material layer 2004. Theforward scattered emitted radiation sub-component 2016 of forwardtransferred down-converted radiation 2010 may be produced byshort-wavelength radiation 2000 impinging on particles of the downconversion material 2004 and that also bounces back and forth on theparticles of the down conversion material 2004 before being transmittedthrough the down conversion material 2004.

One of the sub-components of back transferred down-converted radiation2012 may be emitted radiation 2020; i.e., down-converted radiationhaving a longer wavelength than the short-wavelength radiation 2000 thatimpinges onto the down conversion material layer 2004. The emittedradiation sub-component 2018 of back transferred down-convertedradiation 2012 may be produced by short-wavelength radiation 2000impinging on particles of the down conversion material 2004 as it isreflected from the down conversion material 2004. The secondsub-component of back transferred down-converted radiation 2012 may beback scattered emitted radiation 2020; i.e., other down-convertedradiation having a longer wavelength than the short-wavelength radiation2000 that impinges onto the down conversion material layer 2004. Theback scattered emitted radiation sub-component 2020 of back transferreddown-converted radiation 2012 may be produced by short-wavelengthradiation 2000 impinging on particles of the down conversion material2004 and that also bounces back and forth on the particles of downconversion material 2004 before being reflected from the down conversionmaterial 2004.

White light may be produced by the combinations of the variouscomponents discussed above. In the forward transferred direction (i.e.,for radiation 2008, 2014, 2016, 2010 that is transmitted through thedown conversion material layer), white light may be produced by thecombination of forward transferred short-wavelength radiation 2008 witheither or both of the sub-components 2014, 2016 of the forwardtransferred down-converted radiation 2010. That is, white light may beproduced in the forward transferred direction by the combination offorward transferred short-wavelength light 2008 with transmitted emittedradiation 2014 and/or with transmitted forward scattered emittedradiation 2016.

In the back transferred direction (i.e., for radiation 2006, 2018, 2020,2012 that is reflected from the down conversion material layer), whitelight may be produced by the combination of back transferredshort-wavelength radiation 2006 with either or both of thesub-components 2018, 2020 of the back transferred down-convertedradiation 2012. That is, white light may be produced in the backtransferred direction by the combination of back transferredshort-wavelength light 2006 with reflected emitted radiation 2018 and/orwith reflected back scattered emitted radiation 2020.

The wavelength of the forward transferred short-wavelength radiation2008 may be about the same as the wavelength of the radiation 2000emitted by a radiation source such as an LED chip 2002. The wavelengthof the back transferred short wavelength radiation 2006 may be about thesame as the wavelength of the radiation 2000 emitted by the radiationsource 2002. The wavelength of the forward transferred short-wavelengthradiation 2008 may be about the same as the wavelength of the backtransferred short-wavelength radiation 2006. In an exemplary embodiment,the radiation source 2002 may emit radiation exhibiting a wavelengththat is less than 550 nm, more particularly in a range of about 200 nmto less than 550 nm. Accordingly, the wavelength of the forwardtransferred short-wavelength radiation 2008 and the wavelength of theback transferred short-wavelength radiation 2006 may be less than 550nm, more particularly in a range of about 200 nm to less than 550 nm.

The wavelength of the forward transferred down-converted radiation 2010(including its sub-components 2014, 2016) and the wavelength of the backtransferred down-converted radiation 2012 (including its sub-components2018, 2020) may be any wavelength that is longer that the excitationspectrum of the down conversion material 2004. In an exemplaryembodiment, the excitation spectrum of the down conversion material 2004may be in the range of about 300 nm to about 550 nm. In alternativeembodiments, other down conversion materials may be used that have anexcitation spectrum other than in the range of about 300 nm to about 550nm. The excitation spectrum of the down conversion material 2004 shouldproduce radiation having a wavelength that is longer than the wavelengthof the radiation produced by the short-wavelength emitting radiationsource 2002. In an exemplary embodiment, the down conversion material2004 may produce radiation in the range of from about 490 nm to about750 nm.

However, if the LED chip 2002 does not emit short-wavelength radiation,or if the wavelength of radiation emitted by the LED chip is greaterthan the excitation spectrum of the down-conversion material, thedown-conversion material layer 2004 behaves like a diffuser element.Therefore, only two components may be produced by the down conversionmaterial 2004: forward transferred radiation 2008 transmitted throughthe down-conversion material 2004, and back transferred radiation 2006reflected from the down-conversion material 2004.

The inventors have discovered that the performance of phosphor convertedLEDs is negatively affected when placing the down-conversion phosphorclose to the LED die. Poor performance is mainly due to the fact thatthe phosphor medium surrounding the die behaves like an isotropicemitter, and some portion of the back transferred radiation towards thedie circulates between the phosphor layer, the die, and the reflectorcup. As a result, the back transferred radiation increases the junctiontemperature, thus reducing system efficacy and increasing the yellowingof the encapsulant. All of these factors reduce the light output overtime.

The literature shows that 60 percent of the light impinging on thephosphor layer is back transferred, contributing to the describedeffects (Yamada, et al., 2003). Lab measurements of eight YAG:Cephosphor plates proved that nearly 60% of the radiant energy istransferred back in the direction of the blue LED source. The absolutemagnitude of the radiant energy reflected depends, among other factors,on the density of the phosphor coating. FIG. 1 shows the measuredreflected spectral power distribution 2 of a blue LED with a YAG:Cephosphor plate. FIG. 1 also shows the measured transmitted spectralpower distribution 4 of the same arrangement. As shown, most of thelight is reflected back and not transmitted forwardly.

Such effects are expected to be of a higher magnitude in RCLEDs, becausetheir light output is much more collimated. Consequently, the packagingattempts to capture the transmitted, emitted, and reflected componentsto improve system efficiency. Additionally, the inventors have createdpackaging that allows the phosphor layer to be moved away from the die,preventing radiation feedback into the LED and RCLED. As a result, thepackaging increases the efficiency of the device by allowing more of theradiation reflected off and emitted by the phosphor layer to exit thedevice. At the same time, radiation from the RCLED impinges on thephosphor layer uniformly to obtain a uniform white light source. Inaddition, the life of the LED and RCLED is improved

In traditional phosphor-converted white LEDs, where the phosphor isplaced adjacent the die, more than 65% of the light generated by thephosphor is back-scattered and lost within the LED package. Based onthese findings, a technique referred to as Scattered Photon Extraction™(SPE™) has been developed. An aspect of the technique has been disclosedin pending International Application No. PCT/US2005/015736 filed on May5, 2005 and published as WO 2005/107420 A2 on Nov. 17, 2005.

To increase the light output from a phosphor-converted white LED(pc-LED) and to achieve higher luminous efficacy, the down-conversionmaterial (e.g., phosphor or quantum dots) is removed to a remotelocation and a properly tailored optic device is placed between the LEDchip and the down-conversion material layer. Then, the back transferredlight can be extracted to increase the overall light output andefficacy. This technique significantly increases the overall lightoutput and luminous efficacy of a pc-white LED by extracting thephosphor emitted and back scattered reflected radiation, and thereflected short-wavelength radiation that otherwise would be lost.

FIGS. 2 and 3 illustrate a first exemplary embodiment of the inventionusing the SPE™ concept. FIG. 2 illustrates a high efficiency lightsource that uses solid state emitter(s) and down conversion material, inaccordance with an exemplary embodiment of the present invention.

This embodiment has a distributing optic, light transmissive, enclosureoptic 10, which has a cylindrical geometry. As shown, enclosure optic 10includes phosphor layer 12 embedded in the middle section of thedistributing optic. This configuration effectively splits thedistributing optic into substantially two equal pieces, or portions.That is, the phosphor layer may be a strip that is substantiallyparallel to a longitudinal axis of cylindrical optic 10.

In one exemplary embodiment, phosphor layer 12 may be a YAG:Ce phosphorlayer. In an alternative exemplary embodiment, the phosphor layer maycomprise other phosphors, quantum dots, quantum dot crystals, quantumdot nano crystals or other down conversion material. It will beunderstood that other embodiments of the present invention may include aphosphor layer that is similar to phosphor layer 12. Unlike the embeddedphosphor layer, shown in FIG. 2, however, other embodiments may have aphosphor layer that is not embedded. Moreover, the phosphor layer neednot be of uniform thickness, rather it may be of different thicknessesor different phosphor mixes to create a more uniform color output.

One or more LEDs or RCLEDs may be placed inside the cylindrical optic ata bottom portion, designated as 14. In an alternative embodiment, one ormore LEDs/RCLEDs may be placed at a location other than at the bottomportion of the cylindrical optic.

Short wavelength radiation 16 is emitted from the LEDs/RCLEDs. Shortwavelength radiation is in the range of 250 nm to 500 nm. Becausephosphor layer 12 is substantially in the middle of the cylindricaloptic, short-wavelength radiation from the LEDs/RCLEDs causesshort-wavelength radiation to impinge from either side of thecylindrical optic onto the phosphor layer 12. The impingement ofshort-wavelength radiation onto the phosphor layer 12 may produceradiation with four components: short-wavelength radiation 18, backtransferred from the phosphor layer 12; short-wavelength radiation 20,forward transferred through the phosphor layer 12; down-convertedradiation 22, back transferred from the phosphor layer 12; anddown-converted radiation 24, forward transferred through the phosphorlayer 12. These four components, which are produced on both sides of thephosphor layer 12, combine and produce white light 26. By using thelight transmissive properties of the cylindrical optic 10, the backtransferred short-wavelength radiation from the phosphor layer 12 andthe down-converted radiation back transferred from the phosphor layer 12may be extracted. Therefore, the overall light output and efficacy of aphosphor-converted white LED device is significantly increased.

As an example, a high-flux blue (470 nm) illuminator LED (Shark series)emitter by Opto Technology may be used. The density of phosphor layer 12may be in the range of 4-8 mg/cm² (other densities are alsocontemplated), the length of cylindrical optic 10 may be in the range of2 to 4 inches, and the diameter of the cylindrical optic may be about0.5 inches. As another example, a different package efficiency anduniformity may be achieved by changing the phosphor-layer density, andthe length and diameter of the cylindrical optic. Better efficiency anduniformity of light along the circumference of the cylindrical optic maybe achieved when the cylindrical optic is 2.25 inches long.

The embodiment shown in FIG. 2 may be formed from half-round acrylic rodsegments that are cut from a fully-round acrylic rod and polished.Phosphor may be mixed with optically clear epoxy and then spreaduniformly on the flat surface of each rod segment. The rod segments maythen be attached together and put into an oven to cure the epoxy.

The overall emission loss for a 2.25 inch optical element (cylindricaloptic) was found to be approximately 16%. The losses included: 6% lightreflected back to the LED, 7% Fresnel loss, and 3% irrecoverable lossdue to mounting hardware.

Approximately half of the losses may be attributed to the Fresnel loss,which occurs at the boundaries between media having different refractiveindices. Fresnel losses may be reduced by using a coupling mechanismbetween the LEDs/RCLEDs and the cylindrical optic. In addition, lossesmay be recovered by using an anti-reflective coating on the LEDs/RCLEDsto prevent light from reflecting back to the LEDs/RCLEDs.

FIG. 3 is a cross-sectional view of the cylindrical optic, at the bottomportion, designated as 14. As shown, cylindrical optic 10 includes twohalf-round acrylic rod segments 14 a and 14 b. Phosphor layer 12 issandwiched between acrylic rod segment 14 a and acrylic rod segment 14b. Each acrylic rod segment includes short wavelength radiation emittingsources 17 and 19. Short wavelength radiation emitting sources 17 and 19may each be a semiconductor short wavelength radiation emitting diode,such as a light emitting diode (LED), a laser diode (LD), or a resonantcavity LED (RCLED). It will be understood that one or more than twolight emitting sources may be included in bottom portion 14. As such,there may be an array of multiple light emitters disposed within acrylicrod segment 14 a and another array of multiple light emitters disposedwithin acrylic rod segment 14 b. These arrays may be arrangedsymmetrically with respect to each other, in a manner that is similar tolight sources 17 and 19, which are shown disposed symmetrically aboutphosphor layer 12 of FIG. 3.

FIGS. 2A and 2B illustrate another embodiment of the present inventionhaving the distributing optic, light transmissive enclosure 10. FIG. 2Ais an alternative embodiment of a high efficiency light source that usesmultiple colored light emitting sources and down conversion material.FIG. 2B is a cross-sectional view of a bottom portion of the highefficiency light source shown in FIG. 2A.

In one exemplary embodiment, down conversion material 12 may besandwiched between two diffuser layers 20 and 22. The embodimentillustrated in these figures also uses the SPE™ technique. In thisembodiment, and in all embodiments disclosed herein, the down conversionmaterial 12 may comprise one or more phosphors such as YAG:Ce; YAG:cephosphor plus Eu phosphor; YAG:Ce phosphor plus cadmium-selenide (CdSe);or other types of quantum dots created from other materials includinglead (Pb) and Silicon (Si); and other phosphors that have beenidentified in a copending PCT application filed on Jun. 20, 2006(Attorney Docket RPI-143WO). In other alternative embodiments, thephosphor layer may comprise other phosphors, quantum dots, quantum dotcrystals, quantum dot nano crystals, or other down-conversion materials.In any embodiment or alternative embodiment, the down conversion regionmay be a down conversion crystal instead of a powdered material mixedinto a binding medium.

One or both of the diffuser layers 20, 22 may be a microlens layer ormicro or nano scattering particles diffused in polymer or other materialhaving the characteristics of beam control for the forward transferredand back transferred radiation. Both the phosphor layer 12 and thediffuser layers 20 and 22 may be embedded in the middle section of thedistributing optic 10, as if splitting the distributing optic 10 intosubstantially two equal pieces, or portions. That is, the phosphor layer12 and the diffuser layers 20, 22 may be substantially parallel to alongitudinal axis of the distributing optic 10. In an alternativeembodiment, neither the phosphor layer 12 nor the diffuser layers 20, 22need to be embedded. In an exemplary embodiment, the phosphor layer 12may be bonded to the diffuser layers 20, 22. In an alternativeembodiment, the phosphor layer 12 need not be bonded to the diffuserlayers 20, 22.

Phosphor layer 12 and diffuser layers 20, 22 need not have therectangular shape illustrated in FIGS. 2A and 2B. In alternativeembodiments, the diffuses layers 20, 22 may be curved, round, square,triangular, or other shapes. In addition, their shapes may change alongthe longitudinal axis of the distributive optic 10. Furthermore, therespective sizes (respective lengths or widths) of the phosphor layer 12and the diffuser layers 20, 22 need not be the same. For example, thelength or width of the phosphor layer 12 may be different than one orboth of the diffuser layers 20, 22.

In yet another alternative embodiment, a single diffuser layer may bedisposed in between two phosphor layers. In still another alternativeembodiment, a diffuser layer may be disposed in the distributing opticwithout any phosphor layer.

A radiation source 24 may comprise a plurality of light emitting sourcesthat may emit multiple color radiation. That is, each of the pluralityof light emitting sources may exhibit a spectrum that is different froma spectrum of at least one of the other light emitting sources. Each ofthe light emitting sources 24 may be one or more LEDs, or one or moreLDs (laser diode), or one or more RCLEDs. Any of the embodimentsdescribed herein may be one or more of these types of diodes. Theplurality of multiple colored light emitting sources 24 may be mountedon a board or substrate 14 so that the LEDs 24 are disposed within theconfines of the distributing optic 10 when the distributing optic 10 ismounted on the board 14. That is, the multi-colored LEDs 24 may beplaced on board 14 so that they are inside the distributing optic 10when the bottom of the distributing optic 10 is mounted on board 14.

In this exemplary embodiment, and in all of the embodiments disclosed inthis application, individual ones of the LEDs 24 may exhibit one or moreof the colors red, green, and blue. For example, if three LEDs are usedin this embodiment, one LED may emit red light, a second LED may emitgreen light, and the third LED may emit blue light. That is, each of theLEDs (sometimes referred to as chips) may produce its own respectivenarrow band of radiation, or may produce both narrow bands and widebands of radiation. In an alternative embodiment, one or more of theLEDs may display a color other than red, green, or blue. Although FIGS.2A and 2B illustrate three LEDs, alternative embodiments may use feweror more LEDs. In addition, the number of LEDs placed on each side of thephosphor layer 12 may be the same or may be different. All of theembodiments of the device may mix multiple spectra to create white lightor may create various shades of colors with uniform illumination andcolor without reducing the overall luminous efficiency.

The colors that may be displayed by the LEDs in any embodiment maydepend upon the use to which the device is put. In some embodiments,multiple colors may be used. In other embodiments, only two colors maybe used. In some embodiments more than one LED may emit a particularcolor. Even if the multiple colored light emitting sources 24 arecapable of emitting a plurality of colors, all of the colors need not beemitted in every embodiment. Instead, only some of the colors may beemitted in a particular embodiment or the hue of a particular color maybe modified in ways that are known to one of ordinary skill in the art.The use of LEDs emitting different colors and the use of techniques thatmay modify the hue of one or more colors may enable one to dynamicallychange the emitted colors based upon a user's needs.

As illustrated in FIG. 2B, some of the multiple colored light emittingsources 24 may be placed adjacent a first side 12A of the phosphor layer12 and others of the multi-colored LEDs 24 may be placed adjacent asecond side 12B of the phosphor layer 12. Each of the multiple coloredlight emitting sources 24 may be placed at one or more predetermineddistances from the phosphor layer 12.

In an alternative embodiment of FIGS. 2A and 2B, the multiple coloredradiation emitting sources 24 may be placed at a location other than onboard 14 or may be placed at a location other than at the bottom of thedistribution optic 10. In another alternative embodiment, multi-coloredLEDs may be placed adjacent both ends 15, 16 of the distributing optic10. In yet other alternative embodiments, the phosphor layer 12 may beused without one or more of the diffuser layers 20, 22 or one or more ofthe diffuser layers 20, 22 may be used without phosphor layer 12.

FIG. 4 illustrates another exemplary embodiment of the invention usingthe SPE™ technique. It illustrates another high efficiency light sourcethat may use multiple solid state emitters and down conversion material.This embodiment may be used in interior spaces where general ambientlighting is required. As shown, the device includes phosphor plate 50(for example YAG:Ce or other phosphors, as enumerated previously). Thedevice also includes multiple semiconductor short wavelength radiationemitting diodes 56 forming an array, such as LED/RCLED array 52. Thearray 52 is mounted on substrate 54 that may be of aluminum material. Inan exemplary embodiment, substrate 54 may be circular. In the exemplaryconfiguration illustrated in FIG. 4, the LEDs/RCLEDs are arranged in aspaced relation to each other and placed around the circular substrate.

The array of short wavelength radiation emitting diodes are placed onthe substrate so that the radiation emitting surfaces of the diodes facetoward phosphor layer plate 50. In this manner, diodes 56 emit shortwavelength radiation toward phosphor layer plate 50. As the shortwavelength radiation impinges on the phosphor layer plate, the fourcomponents of radiation discussed above may be produced: shortwavelength back transferred radiation and back transferreddown-converted radiation 60; and short wavelength forward transferredradiation and forward transferred down-converted radiation 64. The shortwavelength back transferred radiation and back transferred downconverted radiation 60 produces white light 62. The forward transferredshort wavelength radiation and forward transferred down-convertedradiation 64 produces white light 66.

FIGS. 5A and 5B illustrate another exemplary embodiment of the inventionusing the SPE™ technique. It is another embodiment of a high efficiencylight source that uses solid state emitter(s) and down conversionmaterial. FIG. 5B is a cross-sectional view of the high efficiency lightsource shown in FIG. 5A. As shown, device 500 includes cup 502, and oneor more light emitters 501 disposed within cup 502 at a base of cup 502.Also included are phosphor layers 503 and 504. Phosphor layer 504 isdisposed at the opposite end from the base of light emitter 501 and at asubstantial center from the walls of cup 502. Phosphor layer 503 isdeposited on the inside of the walls of cup 502. The embodiment shown inFIGS. 5A and 5B may be used in interior spaces where general ambientlighting is required.

The device 500 includes cup 502 which may be a transparent cup havingone LED/RCLED or multiple LEDs/RCLEDs emitting short wavelengthradiation arranged in an array. The cup includes one phosphor layer 503bonded to the inside transparent wall of cup 502. The other phosphorlayer 504 may be bonded only at the center area of the cup. Accordingly,most of the back transferred short wavelength radiation and backtransferred down-converted radiation may exit directly from thetransparent portion of the front surface. Narrow beams of emitted lightfrom the LED/RCLED are preferred in this embodiment to minimize shortwavelength radiation from the LED/RCLED directly exiting the transparentportion of the front surface without impinging on the phosphor layer.The cup may be made of glass or acrylic.

The inside portion of cup 502 may be filled with glass or acrylicmaterial, thereby sandwiching phosphor layer 503 between cup 502 and theinside portion contained within cup 502. Phosphor layer 504 may also bebonded onto the exterior surface of the glass or acrylic material. In analternate embodiment, phosphor layer 504 may be placed within the glassor acrylic material, in a manner similar to that described for thephosphor layer sandwiched between two half-round acrylic rods, shown inFIGS. 2 and 3.

FIG. 6 illustrates yet another exemplary embodiment of the inventionusing the SPE™ technique. It illustrates another high efficiency lightsource that uses solid state emitter(s) and down conversion material. Itillustrates an optic device making use of a down conversion materialthat is remote from a short wavelength radiation emitter. The downconversion material may be a phosphor. As shown, device 600 includesshort wavelength radiation emitter 602 separated from phosphor layer 604by optic device 606 which may be made of a substantially transparentmedium that may be substantially light transmissive. In an exemplaryembodiment, the substantially transparent medium may be air. In analternative embodiment, the substantially transparent medium may beglass or acrylic. Phosphor (or quantum dot) layer 604 may be mounted ordeposited on a portion of optic device 606 having substantiallytransparent and substantially light transmissive walls 610 and 612.Phosphor (or quantum dot) layer 604 may include additional scatteringparticles (such as micro spheres) to improve mixing light of differentwavelengths. Also, the phosphor (or quantum dot) layer 604 may be ofsingle phosphor (or quantum dot) or multiple phosphors (or quantum dots)to produce different colored down-converted radiation that may be inseveral different spectral regions. Alternatively, a layer withscattering particles only may be placed above, or below, or above andbelow the down conversion material layer to improve color mixing.

In an exemplary embodiment, the portion of optic device 606 upon whichphosphor layer 604 may be deposited may be an end 618 of optic device606. Radiation emitter 602 may be located at another portion of opticdevice 606. In an exemplary embodiment, radiation emitter 602 may belocated at another end 620 of optic device 606. Each of walls 610 and612 of optic device 606 may be a continuous wall, if optic device 606has a circular cross-section.

Short wavelength radiation emitter 602 may be located between walls 610and 612. Both the short wavelength radiation emitter 602 and the opticdevice 606 may be positioned on a base 603. Radiation rays 614 maycomprise radiation transmitted through phosphor layer 604 includingforward transferred short-wavelength radiation transmitted though thephosphor layer 604 and forward down-converted radiation transmittedthrough the phosphor layer 604.

Exemplary radiation rays 615 may comprise back transferredshort-wavelength radiation and back transferred down-converted reflectedradiation that may be emitted and/or scattered back by phosphor layer604. Radiation rays 616 may comprise the radiation scattered back byphosphor layer 604. Radiation rays 616 may comprise the radiation rays615 that may be transmitted through the substantially transparent,substantially light transmissive walls 610 and 612. Although exemplaryarrows 615 show back transferred radiation being transferred around themiddle of side walls 610 and 612, it will be understood that backtransferred radiation may be transferred through side walls 610 and 612at multiple locations along the side walls 610 and 612. The transfer ofradiation outside the optic device 606 may be referred to as extractionof light. Accordingly, both radiation rays 615 and radiation rays 616may include short-wavelength radiation reflected from the phosphor layer604 and down-converted reflected radiation that may be emitted and/orscattered from the phosphor layer 604. Radiation rays 616 may alsoinclude radiation from radiation emitter 602. In an exemplaryembodiment, some or all of radiation rays 615 and/or 616 may be seen asvisible light.

The transfer (extraction) of radiation through side walls 610 and 612 tothe outside of optic device 606 may occur because optic device 606 maybe configured and designed with substantially transparent, substantiallylight transmissive walls 610 and 612 to extract radiation from insideoptic device 606 to outside optic device 606. In addition, variouswidths of optic device 606 may be varied in order to extract a desiredamount of radiation out of the optic device 606. The widths that may bevaried are the width at the end 618 and the width at the end 620.Similarly, widths of optic device between end 618 and end 620 may bevaried. The variation of widths of optic device 606 between ends 618 and620 may be effected by walls 610 and 612 being substantially straight,curved, or having both straight and curved portions.

The dimensions of the features of the optic device 606 discussed abovemay be varied depending upon the application to which the optic device606 may be used. The dimensions of the features of optic device 606 maybe varied, and set, by using the principles of ray tracing and theprinciples of total internal reflection (TIR). When principles of TIRare applied, reflectivity of radiation off of one or both of walls 610and 612 may exceed 99.9%. The principles of TIR may be applied to all ofthe embodiments disclosed in this application.

In one embodiment of optic device 606, for example, the dimensions ofoptic device 606 may be set in order to maximize the amount of theradiation from radiation source 602 that enters into optic device 606.In another embodiment, the dimensions of optic device 606 may be set inorder to maximize the amount of radiation from radiation source 602 thatimpinges upon down conversion material 604. In yet another embodiment,the dimensions of optic device 606 may be set in order to maximize theamount of radiation that is back transferred from down conversionmaterial 604. In still another embodiment, the dimensions of opticdevice 606 may be set in order to maximize the amount of radiation thatis extracted through walls 610 and 612. In another embodiment, thedimensions of optic device 606 may be set in order to provide a devicethat, to the extent possible, simultaneously maximizes each of theradiation features discussed above: the amount of radiation enteringinto optic device 606; the amount the amount of radiation that impingesupon down conversion material 604; the amount of radiation that is backtransferred from down conversion material 604; and the amount ofradiation that is extracted through walls 610 and 612. In still anotherembodiment, the dimensions of optic device 606 may be set so that any orall of the features discussed above are not maximized. The principles ofray tracing and the principles of TIR may be used in order to implementany of these embodiments.

The principles discussed with respect to the embodiment illustrated inFIG. 6 may also be applied to all of the embodiments illustrated anddiscussed herein.

As indicated above, radiation source 602 may be an LED, an RCLED, or alaser diode (LD). If an LD is used as radiation source 602, all of theradiation from the LD may directed to, and may impinge upon, the downconversion layer 604. Accordingly, when an LD is used, the shape of theoptic device 606 may be in the shape of a cylinder because substantiallynone of the back transferred radiation may bounce back toward the LD andsubstantially all of the back transferred radiation may be extractedthrough the sides of the cylinder.

FIG. 7 illustrates yet another exemplary embodiment of the inventionusing the SPE™ technique. FIG. 7 depicts a reflector at least partiallysurrounding the high efficiency light source shown in FIG. 6, forredirecting the rays emitted from the light source(s). As shown, device700 includes device 600 disposed within reflector 702. Reflector 702 hasa geometric shape of a parabola for illustration purposes. The inventionis not so limited in that reflector 702 may have other geometricalshapes, such as a cone, a sphere, a hyperbola, an ellipse, a pyramid, ormay be box-shaped, for example. Advantages of device 700 may includebetter control of the beam output distribution and better uniform outputof the color. Whenever a reflector is illustrated in any of theembodiments disclosed herein, the shape of the reflector may be any ofthese shapes.

Substrate 603 may be used for mounting the short wavelength radiationemitting source (602), one end of optic 606, and one end of reflector702, as shown in FIGS. 6 and 7.

Light rays 616 may impinge on reflector 702 which may redirect themforward as light rays 714. Advantageously, the direction of light rays714 are desirably generally in the same direction as radiation rays thatmay be transmitted through the phosphor layer. Consequently, the totallight output of the device 700 may be a combination of radiationtransmitted through the phosphor layer and light rays 714. As indicatedin the discussion of the embodiment illustrated in FIG. 6, theprinciples of TIR may also be applied to the embodiment illustrated inFIG. 7. Light that escapes from optic device 606 may be captured byreflector 702. Some of the light captured by reflector 702 may beredirected by reflector 702 in the direction generally indicated byarrow 714 and some of the light may be redirected back into optic device606. The effects described herein of combining the principles of TIRwith is the use of a reflector may apply to all embodiments illustratedin this application that use a reflector.

Similar to the other embodiments of the invention, short wavelengthradiation emitting source 602 may be one or multiple semiconductor shortwavelength radiation emitting diodes, such as an LED, LD or RCLED. Theshort wavelength radiation emitting diodes may be mounted in an array ofdiodes, similar to the array of light sources depicted as array 52 inFIG. 4. In addition, phosphor layer 604 may be similar to phosphor layer50 depicted in FIG. 4.

FIG. 7A illustrates another exemplary embodiment of the invention usingthe SPE™ technique. The exemplary embodiment illustrated in FIG. 7A usesmultiple colored radiation emitting sources. As shown, device 710includes optic device 704 disposed within reflector 702. Optic device704 may have substantially transparent walls 707 and 708. Downconversion material layer 706 and diffuser layer 705 may be mounted ordeposited on a portion of optic device 704 that may be an end 714 ofoptic device 704. Reflector 702 may be used to control the output beamdistribution of the device 710 as well as to achieve uniform coloroutput from the device 710. Optic device 704 and reflector 702 may bothbe mounted onto substrate 703. Substrate 703 may provide an electricalconnection and/or heat dissipation for light sources. In an alternativeembodiment, optic device 704 may be used without reflector 702.

The embodiment illustrated in FIG. 7A may have multiple coloredradiation emitting sources 701. The nature of the multiple coloredradiation emitting sources 701 may be the same as described elsewhere inthis application with respect to other embodiments of this invention.The multiple colored radiation emitting sources 701 may be located on aportion of the optic device 704 that may be at an end 712 of the opticdevice 704. As stated, down conversion material layer 706 and a diffuserlayer 705 may be located at another end 714 of the optic device 704. Thecharacteristics of the down conversion material layer 706, thecharacteristics of the diffuser layer 705, and the number of layerscomprising the down conversion material layer 706 and the diffuser layer705 may be the same as described elsewhere in this application withrespect to other embodiments of this invention. As described elsewherein this application, for example, the down conversion material layer 706may be a phosphor layer. The optic device 704 may be a substantiallytransparent medium or other medium described elsewhere in thisapplication with respect to other embodiments of this invention. Forexample, optic device 704 may be made of glass, or acrylic, or polymer,or silicon or any other material that is substantially lighttransmissive.

It will be understood by those skilled in the art that phosphor layer706 may also affect light in the same way that a diffuser layer affectslight by providing uniformity to the light. That is, phosphor layer 706may also function as a diffuser. The additional diffuser layer 705therefore may make the light more uniform than the light may be if aphosphor layer 706 is used alone. In other embodiments, the positions ofthe phosphor layer 706 and the diffuser layer 705 can be switched. Thatis, phosphor layer 706 may be located on top of the optic device 704 anddiffuser layer 705 may be located on top of the phosphor layer 706. Inyet another embodiment, phosphor layer 706 may be used without diffuserlayer 705. In still another embodiment, diffuser layer 705 may be usedwithout phosphor layer 706. Regardless of whether a phosphor is usedalone, a diffuser is used alone, or both a phosphor and a diffuser areused together, the purpose of using one or both of them may be toprovide uniformity to the light and uniformity to any colors that may beemitted by the radiation emitting sources 701.

FIGS. 7B-7D illustrate different ways of dispersing the down conversionmaterial 706 used in the embodiment illustrated in FIG. 7A and with allof the other embodiments illustrated herein. As illustrated in FIG. 7B,down conversion materials such as phosphor may be uniformly dispersedwithin the down conversion material layer 706.

As illustrated in FIG. 7C, the down conversion material layer 706 maycomprise a plurality of down conversion materials. Each one of theplurality of down conversion materials may have different densities ofdown conversion materials depending on the distance from the center ofthe layer of down conversion material. For example, down conversionmaterial layer 706 may have four segments, each of the segments have adifferent density. A first segment of down conversion material 706Ahaving a first density of down conversion material may be at the centerof the down conversion material layer 706. A second segment of downconversion material 706B having a second density of down conversionmaterial may surround the first segment of down conversion material706A. A third segment of down conversion material 706C having a thirddensity of down conversion material may surround the second segment ofdown conversion material 706B. A fourth segment of down conversionmaterial 706D having a fourth density of down conversion material maysurround the third segment of down conversion material 706C. Althougheach of the aforesaid segments of down conversion material are shown ashaving a circular shape, each of the segments may each have differentshapes. For example, they could be in the shape of a square, a triangle,or other polygonal shape or any shape other than polygonal. In addition,more or fewer segments of down conversion material may be used.

A different way of dispersing down conversion material is illustrated inFIG. 7D. As shown in FIG. 7D, specs or “sesame dots” (that is, smallpieces) of down conversion material may be dispersed about the secondaryoptic device. For example, the specs of down conversion material may bedeposited on top of the secondary optic device 708 or may be embeddedwithin the top surface at end 714 of the secondary optic device 704. Thespecs of down conversion material may be randomly dispersed or may bedispersed in a predetermined pattern.

The embodiments of a phosphor disclosed in FIGS. 7B to 7D along withother embodiments of phosphors discussed elsewhere in this applicationmay be used to adjust phosphor density in order to obtain a desiredcolor and hue. Such adjustments may be made with any embodimentdisclosed in this application whether the embodiment is intended toproduce white light or light of a particular color. For example, anembodiment may use a mixture of blue and yellow phosphors. Analternative embodiment may use a mixture of multiple kinds of phosphorssuch as quantum dots, quantum dot crystals, and quantum dot nanocrystals. Still other embodiments may use a blue LED either with asingle phosphor or a blue LED with multiple phosphors in order to obtaindifferent tones of white light. Still other embodiments may use multiplecolor LEDs with a diffuser. Additional embodiments may use anycombination of these features.

As indicated elsewhere in this application, respective ones of theradiation emitting sources 701 may emit blue light, green light, or redlight in any combination. Different hues of each color may also be used.If one or more of the radiation emitting sources 701 emits blue light,and if the layer 706 is a phosphor, the blue light may be down convertedas described elsewhere in this application resulting in the fourcomponents of radiation described elsewhere in this application. If oneor more of the radiation emitting sources 701 emits blue light, and ifthe layer 706 is not a phosphor but is a different kind of diffusermaterial, the blue light impinging on the layer 706 may not be downconverted. If one or more of the radiation emitting sources 701 emitsred light or emits green light, or emits light of any color other thanblue, such light may not be down converted whether layer 706 is aphosphor material or other diffuser material. If blue light, greenlight, and red light all impinge on layer 706 when a phosphor is used,white light may result depending upon the density of the phosphor.

Regardless of what colors are respectively emitted by the radiationemitting sources 701, and regardless of whether a phosphor or anotherdiffuser material is used, when light from the radiation emittingsources 701 impinges on the phosphor or other diffuser material, forwardtransferred radiation and back transferred radiation results. In thecase of blue light impinging on a phosphor layer, the resultingcomponents of radiation may be as described with respect to FIG. 14. Inthe case of other colors impinging on a phosphor layer, the forwardtransferred light and the back transferred light may be the same coloras the impinging light. For example, if red light impinges on phosphorlayer 706, the forward transferred light and the back transferred lightmay also be red light. The same result would obtain with green light, orany other color besides blue. The same results may obtain if a diffusermaterial other than phosphor is used.

FIGS. 8A through 8E depict different cross-section shapes of the opticelement that may be used with the embodiments of the SPE™ techniquedescribed herein. Optic element 801 illustrated in FIG. 8A is of aconical geometry having a top surface 8012. Alternative optic element802 illustrated in FIG. 8B is of a spherical geometry having a topsurface 8022. Alternative optic element 803 illustrated in FIG. 8C is ofa hyperbolic geometry having a top surface 8032. Alternative opticelement 804 illustrated in FIG. 8D may have conical walls and a concavetop surface 8042. Alternative optic element 805 illustrated in FIG. 8Emay have conical walls and a convex top surface 8052. Other geometricalshapes may include a parabolic or elliptical shape. In addition, the topof the wider surface of each optical element may be flat, or may haveanother geometrical shape.

Similar to the other embodiments, optic elements 801 through 805 may bemade of a substantially transparent material, thereby functioning likean optical lens (similar to optic device 606 of FIG. 6).

Although not shown in FIGS. 8A to 8E, a reflector (similar to reflector702, shown in FIG. 7) may be positioned to surround each optical element801 through 805. Furthermore, each optical element 801 through 805 mayinclude a down-conversion material layer and a diffuser layer (similarto phosphor layer 706 and diffuser layer 705 shown in FIG. 7A). Thisphosphor layer and diffuser layer (not shown in FIGS. 8A to 8E) may bedeposited on top one of the respective top surfaces 8012, 8022, 8032,8042, 8052 of each optical element, opposite to its respective lightemitting source. Alternatively, this phosphor layer and diffuser layer(not shown in FIGS. 8A to 8E) may be sandwiched within each opticalelement, near one of the respective top surfaces 8012, 8022, 8032, 8042,8052 of the respective optical elements and opposite to its respectivelight emitting source. In other embodiments, as discussed with respectto FIG. 7A, the positions of the phosphor layer 706 and the diffuserlayer (not shown in FIGS. 8A to 8E) be switched. That is, phosphor layer706 may be located on top of a respective one of the optic devices 801,802, 803, 804, 805 and a diffuser layer (not shown in FIGS. 8A to 8E)may be located on top of the phosphor layer 706. In yet anotherembodiment, phosphor layer 706 may be used without a diffuser layer. Instill another embodiment, a diffuser layer (not shown in FIGS. 8A to 8E)may be used without phosphor layer 706.

FIGS. 8F and 8G illustrate the embodiments of invention using the SPE™technique includes respective radiation sources, respective reflectors,and an optic device that may exhibit one of the cross-section shapes 801through 805 illustrated in FIGS. 8A to 8E. In FIG. 8F, a reflector 806and a secondary optic device 810 are both revolved objects with a commoncentral axis (not shown). In FIG. 8G, a reflector 812 and an opticdevice 814 are both extruded along their respective long axis. Thesectional view of reflectors 806 and 812 may have a cross-section shapeof a parabola, or other geometrical shapes, such as a cone, a sphere, ahyperbola, an ellipse, a pyramid, or may be box-shaped, for example.

Referring next to FIGS. 9A and 9B, there is shown a two dimensionallinear array of lenses, generally designated as 900. As shown in FIG.9A, an array of N×M high efficiency light source devices are arranged ontop of a lightpipe 912. Although lightpipe 912 is illustrated in FIG. 9Aas having a rectangular shape, it will be understood that it may have ashape other than rectangular. Three of the exemplary light sourcedevices are designated as 910, 920 and 930. The remaining light sourcedevices in the N×M array may be identical to any one of the light sourcedevices 910, 920, or 930. In alternative embodiments, lightpipe 912 mayhave a circular shape or another shape. Also in alternative embodiments,the array of lenses may have a is radial placement or may be placed inother patterns.

As best shown in FIG. 9B, each of light source devices 910, 920, 930 mayinclude radiation emitter 902, lens 904 such as optic device 606 and aphosphor layer (not shown), which may be similar to phosphor layer 604of FIG. 6. Also included may be a reflector 906, which may redirecttransmitted and reflected light from radiation emitter 902 towardslightpipe 912.

Lightpipe 912, as shown, may include side 914 abutting light sourcedevices 910, 920, and 930, and another opposing side 916 further awayfrom the light source devices. On top of opposing side 916, there may bea microlens layer 918. The microlens layer may be bonded to thedeposited phosphor layer.

As best shown in FIG. 9C, one or more of the exemplary light sourcedevices 910, 920 and 930 may be similar to device 710 of FIG. 7A,including multiple colored light emitting sources, a lens such as opticdevice 704, a down conversion material layer such as layer 706, and adiffuser layer such as layer 705. For example, in this alternativeembodiment, light source device 910 may include multiple colored lightemitting sources 902, lens 904 such as optic device 704, a downconversion material layer (not shown), which may be similar to downconversion material layer 706 of FIG. 7A, and a diffuser layer (notshown), which may be similar to diffuser layer 705 of FIG. 7A. Alsoincluded may be a reflector 906, which may be similar to the reflector702 of FIG. 7A. Each of the other light source devices may also havemultiple colored light emitting sources, a lens such as the optic devicedisclosed with respect to FIG. 7A, a down conversion material layer anda diffuser layer similar to the elements contained in light sourcedevice 910. In yet another embodiment, optic device 904 may not have adown conversion material layer deposited on it.

Lightpipe 912, as shown in FIG. 9C, includes side 914 abutting exemplarylight source devices 910, 920 and 930, and another opposing side 916further away from the exemplary light source devices. On top of opposingside 916, there may be deposited microlens layer 940.

FIGS. 10A and 10B illustrate another exemplary embodiment of a highefficiency light source, generally designated as 1040, in whichindividual light source devices may be spaced around the edges of alightpipe 1042. As shown in FIG. 10A, several light devices, such asexemplary light source devices 1046, 1048, 1050, and 1052, etc. may beplaced around the edges of lightpipe 1042.

A cross-section of exemplary high-efficient light source 1040 is shownin FIG. 10B. As shown in FIG. 10B, exemplary light source device 1046may be configured to direct light into lightpipe 1042. Lightpipe 1042may include a first side 1062 of light pipe 1042 and a second side 1064.A microlens layer 1066 may be placed adjacent first side 1062 of lightpipe 1042 and another microlens layer 1068 may be placed adjacent secondside 1064 of lightpipe 1042. Although lightpipe 1042 is illustrated ashaving a polygonal shape, it may also have a circular shape or othershape.

In one embodiment of the embodiment illustrated in FIGS. 10A and 10B,each of the exemplary light source devices 1046, 1048, 1050 and 1052 maybe similar to device 700 of FIG. 7, including a short wavelengthradiation emitter, a lens such as an optic device described herein, anda down conversion material layer. For example, exemplary light sourcedevice 1046 may be mounted onto edge 1060 of lightpipe 1042. Exemplarylight source device 1046 may include short wavelength radiation emitter1054, lens 1056 such as optic device 606, and a down conversion materiallayer (not shown), which may be similar to down conversion materiallayer 604 of FIG. 6 or similar to down conversion material layer 706 ofFIG. 7A. Also included may be reflector 1058, which may redirect theback transferred radiation and forward transferred radiation from lens1056 towards the edge 1060 of lightpipe 1042, and into lightpipe 1042.The reflector 1058 may be similar to reflector 702 of FIG. 7. Additionallight source devices may be placed along edge 1060 and along edge 1070.Even more light source devices may be placed along the other two edgesof lightpipe 1042 that are not shown in FIGS. 10A and 10B. All of thelight source devices, other than light source device 1046, may also havea similar short wavelength radiation emitter, a lens, and a downconversion material layer similar to the elements contained in lightsource device 1046. It will be understood that even though FIG. 10Ashows five light source devices along each of edges 1060 and 1070, feweror more light source devices may be used along each of edges 1060 and1070 and along the edges that are not shown in FIG. 10A.

In another alternative embodiment, one or more of the exemplary lightsource devices 1046, 1048, 1050 and 1052 may be similar to device 710 ofFIG. 7A, including multiple colored light emitting sources, a lens suchas an optic device, a down conversion material layer, and a diffuserlayer. In this alternative embodiment, exemplary light source device1046 may include multiple colored light emitting source 1054, lens 1056such as optic device 704, a down conversion material layer (not shown),which may be similar to down conversion material layer 706 of FIG. 7A,and a diffuser layer (not shown), which may be similar to diffuser layer705 of FIG. 7A. Each of the exemplary light source devices shown in FIG.10A may also have a reflector such as exemplary reflector 1058, whichmay be similar to the reflector 702 of FIG. 7A. The reflector mayre-direct light from the multiple colored light emitting sources and theback transferred light from respective down-conversion material ordiffuser layer toward the edge 1060 of lightpipe 1042, and intolightpipe 1042. Each of the other light source devices may also havemultiple colored light emitting sources, a lens, a down conversionmaterial layer and a diffuser layer similar to the elements contained inlight source device 1046 that may transmit their respective light intolightpipe 1042 through respective edges of lightpipe 1042. In anotherembodiment, optic device 1056 may not have the diffuser layer. In yetanother embodiment, optic device 1056 may not have a down conversionmaterial layer deposited on it.

On top of sides 1062 and 1064 of Lightpipe 1042, as shown in FIG. 10B,there may be deposited microlens layer 1066 and 1068.

FIG. 11 illustrates still another exemplary embodiment of the invention.As shown, device 1110 includes a short wavelength radiation source 1100,a lens 1102 which may be any of the optic devices described herein, anda phosphor layer 1104. The phosphor layer may be deposited on top oflens 1102, so that the phosphor layer is away from the short wavelengthradiation source 1100, in a manner that is similar to that shown inFIGS. 6, 7, 7A, for example. The light source/lens/phosphorconfiguration may be at least partially surrounded by a reflector 1106having a high-reflectance. In an exemplary embodiment the measuredreflectance of reflector 1106 may be in the range of 90% to 97%. Inaddition, a high efficiency microlens diffuser 1108 may be placed acrossthe top of reflector 1106. In an exemplary embodiment, the microlensdiffuser may exhibit greater than 95% efficiency. The reflectance ofother reflectors described in this application may be the same as thereflectance of reflector 1106. The efficiency of other diffusersdescribed in this application may be the same as the efficiency ofdiffuser 1108.

FIG. 11A illustrates another embodiment of the invention. FIG. 11A showsa device 1120 which may include multiple colored radiation emittingsources 1122, an optic device 1124, and a down conversion material layer1126. The optic device 1124 may be mounted adjacent the multiple coloredradiation emitting sources 1122. The down conversion material layer 1126may be mounted or deposited on one portion or on one end 1129 of theoptic device 1124 so that the down conversion material layer 1126 isaway from the multiple colored radiation emitting devices 1122. AlthoughFIG. 11A illustrates three multiple colored radiation emitting sources1122, it will be understood that more or fewer multiple coloredradiation emitting sources 1122 may be used for the reasons explainedwith respect to other embodiments illustrated in this application. Thepackage comprising the array of multiple colored radiation emittingsources 1122, the optic device 1124, and the down conversion materiallayer 1126 may be at least partially surrounded by a reflector 1128having a high reflectance. In an exemplary embodiment of thisalternative embodiment, the measured reflectance of reflector 1128 maybe in the range of 90% to 97%. A high efficiency microlens diffuser 1130may be placed across end 1132 of reflector 1128. End 1132 may be open ifa diffuser is not placed across it. In an exemplary embodiment,microlens diffuser 1130 may exhibit greater than 95% efficiency. In analternative embodiment of the embodiment illustrated in FIG. 11A, adiffuser may be used in place of down conversion material layer 1126 anddiffuser layer 1130 may be eliminated. In another embodiment, the sidewalls of optic device 1124 may be painted white in order to improvecolor mixing.

FIG. 12 illustrates yet another exemplary embodiment of the invention.As shown, device 1210 includes short wavelength radiation source 1200facing phosphor layer 1202 and reflector 1206. A substantiallytransparent medium 1204 may fill the space between short wavelengthradiation source 1200 and phosphor layer 1202. In an exemplaryembodiment, phosphor layer 1202 may be in the shape of a parabola, orother curved shape, similar to one of the geometric shapes previouslyenumerated. Reflector 1206 may be spaced away from the phosphor layer1202 and the radiation source 1200. A substantially transparent medium1208 may be used to fill the space between the phosphor layer 1202 andthe reflector 1206. As shown, phosphor layer 1202 is disposed betweenthe light source 1200 and reflector 1206.

FIG. 12A illustrates still another exemplary embodiment of theinvention. As shown, device 1220 in FIG. 12A has a radiation sourcecomprising multiple colored light emitting sources 1222 facing downconversion material layer such as a phosphor layer 1202 and a reflector1206. Phosphor layer 1202 is disposed away from light emitting sources1222. A substantially transparent medium 1204 may be positioned betweenmultiple colored light emitting sources 1222 and down conversionmaterial layer 1202. In an exemplary embodiment, the down conversionmaterial layer 1202 may be in the shape of a parabola or other curvedshape. Reflector 1206 may be spaced away from the down conversionmaterial layer 1202 and the multi-colored LED array 1222. Asubstantially transparent medium 1208 may be present between the downconversion material layer 1202 and the reflector 1206. In thisembodiment, the down conversion material layer 1202 is disposed betweenthe light emitting sources 1222 and the reflector 1206. In analternative embodiment, a diffuser layer may be placed across an end1224 of reflector 1206. End 1224 may be open if a diffuser layer is notplaced across it. In another alternative embodiment, a diffuser layermay be used instead of a down conversion material layer 1202. If adiffuser layer is used instead of a down conversion material layer, adiffuser layer may not be placed across end 1224.

While it is well known that the phosphor used in white light-emittingdiodes (LEDs) backscatters more than half the light emitted, no one todate has shown that this light may be recovered as photons to increasethe overall efficacy of a white light source. The inventors haveexperimentally verified a scattered photon extraction (SPE™) methodprovided by the various embodiments of the invention, that significantlyincreases the overall efficacy of a white light source. At low currents,the SPE™ package showed over 80 lm/W white light with chromaticityvalues very close to the blackbody locus.

Of the different methods available for creating white light, thephosphor-converted emission method is the most common. A firstphosphor-converted white LED uses cerium doped yttrium aluminum garnet(YAG:Ce) phosphor in combination with a gallium nitride (GaN) based blueLED. In a typical white LED package, the phosphor is embedded inside anepoxy resin that surrounds the LED die. Some portion of theshort-wavelength radiation emitted by the GaN LED is down-converted bythe phosphor, and the combined light is perceived as white by the humaneye. Although these products proved the white LED concept and have beenused in certain niche illumination applications, they are not suited forgeneral lighting applications because of their low overall light outputand low efficacy.

To achieve higher luminous efficacy with white LEDs, improvements areneeded at several stages: internal quantum efficiency, extractionefficiency, and phosphor-conversion efficiency. Some researchers havetaken on the challenge of researching the materials and growth aspectsof the semiconductor to improve internal quantum efficiency. Others areexploring shaped chips, photonic crystals, micron-scale LEDs, and othernovel methods to improve light extraction efficiency. Still others areinvestigating new phosphors that have greater down-conversionefficiencies and better optical properties.

Although past literature acknowledges that a significant portion of thelight is backscattered by the phosphor and lost within the LED due toabsorption, to the best of the inventors' knowledge no one to date hasattempted to improve performance by extracting these backscatteredphotons, by way of the SPE™ method, provided by the embodiments of thepresent invention, which significantly increases the overall lightoutput and luminous efficacy of a phosphor-converted white LED byrecovering the scattered photons.

To better understand the interaction between primary short-wavelengthlight and phosphor and to quantify the amount of forward and backwardscattered light, several circular glass plates, 5 cm in diameter, werecoated by the inventors with different densities of YAG:Ce phosphorranging from 2 mg/cm² to 8 mg/cm². These phosphor plates were placedbetween two side-by-side integrating spheres with the phosphor coatingfacing the right sphere. The phosphor material was excited by radiationfrom a 5 mm blue LED placed inside the right sphere 2.5 cm away from theglass plate. A spectrometer measured the light output from each spherethrough the measurement ports. Light output measured from the left andright spheres indicated the amount of light transmitted through andreflected off the phosphor layer, respectively. The spectrometer datawas analyzed to determine the amount of flux in the blue and yellowregions, corresponding to the radiant energy emitted by the LED and theconverted energy from the YAG:Ce phosphor. Experimental results showedthat the spectral power distributions for the transmitted and reflectedradiations are different, especially the amount of blue-to-yellow ratio.The amount of transmitted and reflected radiations depends on thephosphor density, with lower densities resulting in higher percentagesof transmitted radiation. Typically, the phosphor density may becontrolled such that the transmitted blue and yellow light are in thecorrect proportion to produce white light of a suitable chromaticity,which typically places it on or close to the blackbody locus. From thegathered data, it was estimated that about 40% of the light istransmitted when creating a balanced white light, and the remaining 60%is reflected. Yamada et al. found similar results, as reported in K.Yamada, Y. Imai, K. Ishii, J. Light & Vis. Env. 27(2), 70 (2003). In aconventional white LED, a significant portion of this reflected light isabsorbed by the components surrounding the die, one of the reasons forits low luminous efficacy.

A method by which most of the reflected light may be recovered isillustrated in FIG. 13, which shows schematically an LED package withSPE™ implemented. Unlike a typical conventional white LED package, wherethe phosphor is spread around the die, in the SPE™ package of theinvention the phosphor layer is moved away from the die, leaving atransparent medium between the die and the phosphor. An efficientgeometrical shape for the package may be determined via ray tracinganalysis. The geometry of the package plays an important role, and thegeometry shown in FIG. 13 efficiently transfers the light exiting theGaN die to the phosphor layer and allows most of the backscattered lightfrom the phosphor layer to escape the optic. Compared with the typicalconventional package, more photons are recovered with this SPE™ package.Here again the phosphor density determines the chromaticity of the finalwhite light.

It is worth noting that the SPE™ package requires a different phosphordensity to create white light with chromaticity coordinates similar tothe conventional white LED package. This difference is a result of theSPE™ package mixing transmitted and back-reflected light with dissimilarspectra, whereas the conventional package uses predominantly thetransmitted light.

To verify that the SPE™ package shown in FIG. 13 provides higher lightoutput and luminous efficacy, an experiment was conducted with twelveconventional high-flux LEDs, six 3 W blue and six 3 W white, obtainedfrom the same manufacturer. A commercial optic that fit the profilerequirements of the SPE™ package was found, and several were acquiredfor experimentation with the LEDs. Although this optical element did nothave the desired geometry shown in FIG. 13 to extract most of thebackscattered light, it was sufficient to verify the hypothesis. The topflat portion of the experiment's secondary optic was coated with apredetermined amount of YAG:Ce phosphor. The required phosphor densitywas determined in a separate experiment by systematically varying theamount of phosphor density, analyzing the resulting chromaticity, andselecting the density that produced a chromaticity close to that of thecommercial white LED used in the experiment. To compare the performancesof the two packaging concepts, the white LEDs were fitted with uncoatedsecondary optics. The light output and the spectrum of the commercialwhite LEDs were measured in an integrating sphere, and the current andthe voltage required to power the LEDs were also measured. The samemeasurements were repeated for the SPE™ packages, which included blueLEDs fitted with phosphor-coated secondary optics, as shown in FIG. 13.

The average luminous flux and the corresponding average efficacy for theSPE™ LED packages were found to be 90.7 lm and 36.3 lm/W, respectively.The average luminous flux and the corresponding average efficacy for thetypical white LED packages were 56.5 lm and 22.6 lm/W, respectively.Therefore, the SPE™ LED packages on average had 61% more light outputand 61% higher luminous efficacy. The variation of luminous flux andcorresponding efficacy between similar LEDs was small, with a standarddeviation of less than 4%. The SPE™ packages consistently had higherlumen output and higher efficacy compared with the typical conventionalwhite LED packages.

The impact of current on light output and efficacy was also measured ontwo LED packages, one typical white LED and one SPE™ package. These twoLEDs were subjected to the same light output measurement procedure, buttheir input current was decreased from 700 mA to 50 mA in several steps,and the corresponding photometric and electrical data were gathered. Atvery low currents, the SPE™ package exceeded 80 lm/W, compared to 54lm/W for the conventional package.

With the SPE™ package, the backscattered photons are extracted beforethey are absorbed by the components within the LED. It is essential thatthe phosphor layer be placed farther away from the die, and thebackscattered photons be extracted before they undergo multiplereflections within the package. Moving the phosphor away from the diehas an additional benefit: the life of the white LED is also beimproved, as demonstrated in an earlier paper (Narendran, N., Y. Gu, J.P. Freyssinier, H. Yu, and L. Deng. 2004. Solid-state lighting: Failureanalysis of white LEDs. Journal of Crystal Growth 268 (3-4): 449-456).

An alternate method of the present invention to recover a portion of theback transferred radiation is to coat the sides of the secondary opticswith a reflective material, as shown in FIGS. 5A and 5B. Although theefficacy may improve compared to a conventional white LED package, thegain is not as much, because the back transferred radiation bounces backand forth between the phosphor layer and the reflectors, and a goodportion of this radiation is absorbed and lost as heat. A drawback ofthis method is by increasing the path length of the short-wavelengthradiation traveling through the surrounding epoxy material, the epoxydegrades faster and thus shortens the useful life of the white LED.

It will be understood that the geometry of the SPE™ package shown inFIG. 13 is not limited to this specific shape. Alternate shapes may beused to recover the back transferred radiation more efficiently, whileaddressing other design concerns, such as color and life. As oneexample, in the configuration of FIG. 13, the inventors discovered thata preferred size for the top surface diameter is about 20 mm and apreferred size for the height is about 11 mm.

In summary, the present invention recovers the back transferredradiation from the down conversion material layer or the diffuser layer.In addition, the overall light output and the corresponding luminousefficacy of the LED system may be increased significantly compared toits conventional package. At the same time, the optic device may mixmultiple spectra to create white light and other shades of colors whilewith uniform illumination and color. Applications of embodiments of theinvention include general illumination and backlighting.

Although the invention has been described with reference to exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed to include other variants and embodiments of theinvention which may be made by those skilled in the art withoutdeparting from the true spirit and scope of the present invention.

1. A light emitting apparatus comprising: a radiation source for emitting multi-colored radiation; a diffuser material for receiving at least a portion of the multi-colored radiation emitted by the radiation source and converting the multi-colored radiation into forward transferred radiation and back transferred radiation; and an optic device coupled to the diffuser material adapted to receive the back transferred radiation and extract at least a portion of the back transferred radiation from the optic device.
 2. The light emitting apparatus of claim 1, wherein the radiation source comprises a plurality of light emitting sources, each of the light emitting sources exhibiting a spectrum different than a spectrum of at least one of the other light emitting sources.
 3. The light emitting apparatus of claim 2, wherein the plurality of light sources comprises at least one of one of light emitting diodes (LEDs), laser diodes (LDs), and resonant cavity light emitting diodes (RCLEDs).
 4. The light emitting apparatus of claim 2, wherein a first plurality of light emitting sources are disposed adjacent a first side of the diffuser material and a second plurality of light emitting sources are disposed adjacent a second side of the diffuser material.
 5. The light emitting apparatus of claim 2, wherein the plurality of light emitting sources are disposed at a predetermined distance from the diffuser material.
 6. The light emitting device of claim 2, wherein the plurality of light emitting sources is disposed adjacent a first portion of the optic device.
 7. The light emitting device of claim 6, wherein the diffuser material is disposed adjacent a second portion of the optic device.
 8. The light emitting device of claim 7, wherein the diffuser material is disposed over one of a portion of a second end of the optic device or over substantially all of the second end of the optic device.
 9. The light emitting apparatus of claim 2, further comprising a light pipe, wherein the plurality of light emitting sources are disposed about at least a portion of a circumference of the light pipe for directing the light into the light pipe.
 10. The light emitting apparatus of claim 9, further comprising a microlens layer disposed on a side of the light pipe.
 11. The light emitting apparatus of claim 1, wherein the diffuser material for receiving the multi-colored radiation is at least one of a diffuser, a down conversion material, and a microlens.
 12. The light emitting apparatus of claim 11, wherein the down conversion material includes at least one material for absorbing radiation of a first wavelength in a spectral region and emitting radiation of a second wavelength longer than the first wavelength in the spectral region.
 13. The light emitting apparatus of claim 11, wherein the down conversion material comprises one of a layer having substantially uniformly dispersed material, a layer having a plurality of materials each of the plurality of materials exhibiting a respective density, or material dispersed within the optic device.
 14. The light emitting apparatus of claim 11, wherein the diffuser material comprises at least one layer of down conversion material adjacent the diffuser.
 15. The light emitting apparatus of claim 11, wherein the diffuser material comprises at least one layer of down conversion material positioned away from the diffuser.
 16. The light emitting apparatus of claim 1, wherein the diffuser material for receiving the multi-colored radiation comprises a plurality of down conversion materials for absorbing radiation of a first wavelength in a spectral region and emitting radiation of at least a second wavelength in the spectral region longer than the first wavelength.
 17. The light emitting apparatus of claim 1, wherein the diffuser material for receiving the multi-colored radiation comprises at least one of i) a plurality of diffuser layers and ii) a plurality of down conversion material layers.
 18. The light emitting apparatus of claim 1, further comprising a collecting device for collecting at least a portion of the back transferred radiation leaving the optic device.
 19. The light emitting apparatus of claim 18, wherein the collecting device includes a reflector disposed around at least a portion of the optic device.
 20. The light emitting apparatus of claim 19, wherein a shape of the reflector is one of a cone, sphere, hyperbola, parabola, ellipse, pyramid, and box.
 21. The light emitting apparatus of claim 18, wherein the optic device is disposed one of on the collecting device or at a distance away from the collecting device.
 22. The light emitting apparatus of claim 21, wherein the collecting device is disposed adjacent at least two sides of the optic device.
 23. The light emitting apparatus of claim 18, wherein the light source is disposed between the collecting device and the diffuser material.
 24. The light emitting apparatus of claim 1, wherein the diffuser material is dispersed within the optic device.
 25. The light emitting apparatus of claim 1, further comprising a heat dissipation device coupled to the radiation source.
 26. A light emitting apparatus comprising: a radiation source for emitting multi-colored radiation; an optic device configured to receive radiation emitted from the radiation source; a diffuser material disposed on a portion of the optic device receiving at least a portion of the multi-colored radiation received by the optic device and converting the portion of the multi-colored radiation into forward transferred light and back transferred light, wherein the optic device is configured to extract a portion of the back transferred light.
 27. The light emitting apparatus of claim 26, wherein the radiation source comprises a plurality of light emitting sources, each of the light emitting sources exhibiting a spectrum different than a spectrum of at least one other of the other light emitting sources. 